Hottse electric



TRANSFORMER TAP CHANGING DEV IEJEw March 5, 1929. TRAVERS Re. 17,230

Original Filed June 16, 1926 WITNESSES:

v MW INVENTOR hemyfl. Trauer 'a Reissued Mar. 5, 1929.

HENRY A. rnavrms, or FOREST HILLS, rnnnsrnvmrmnssmnon 'ro wnsrmo- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- yams.

rnnnsrormnnrrar-cnmeme DEVICE. V

j Original No. 1,630,363, dated May 81, 1927, Serial No. 116,314, filed J'unelfi, 1926. Application for reissue x i filed April 21, 1928. Serial No. 271,957.

My invention relates to transformer-tapchanging apparatus and particularly to relay systems for protecting such transformers.

One object of my invention is to provide a protective system for an electrical transformer and tap-changing apparatus that shall protect the apparatus from conditions of short circuit within the transformer winding.

Another object of my invention is to provide a difierential protective system for electric transformers and tap-changing apparatus that shall be controlled in accordance with the operation of the tap-changing apparatus.

Another object of my invention is to provide a protective system for electrical transformers and tap-changing apparatus that comprises an auto-transformer, the connections of which shall be controlled in accordance with the operation of the tap-changing apparatus. 1

An electrical transformer is sometimes provided with a difi'erential relay system connecting the primary and'secondary circuits for the purpose of disconnecting it from its supply circuit in the event that the ratio between its input and output becomes of a magnitude that indicates a condition of a shortcircuit between the turns of its winding or a fault to ground. When atransformer having the above specified equipment is equipped also with tap-changing apparatus for varying the voltage ratio between the primary and secondary windings, it becomes necessary to provide means for varying the connections of the relay system in order that such system shall continue to indicate the true ratio between the transformer input and the output. I I accomplish the desired result by providing an auto-transformer in the relay circuit, one winding of which is energized from the primary circuit of the main transformer and the other winding of which is energized from the secondary winding of the main transformer, three suitable current transformers. of fixed ratio, and varying the com nections of the auto-transformer in accordance with the changes in the voltage ratio of the main transformer.

In the accompanying drawings,

Figure 1 is a diagrammatic view of circuits and apparatus embodying my iuven tion; and

interrupter 6 is provided to 33 mounted on a drum 34 of the Fig. 2 is a fragmentary view of a modified form of my invention.

My invention comprises, in general, a main tion.

The primary winding 2 of the main transformer 1 is connected, through a circuit interrupter, 6 to a supply circuit 7,. The circuit with the usual trip- 5 ping coil 8. I

The secondary winding 3 comprises a pair of parallel windings 9' and 11 that are connected, through an" auto-balance transformer system 5, embodying the details of my inveni 12 and the tap-changing device 4, to a secondary circuit v13. The windin '9 and 11 are provided with a plurality o taps 14 to 23 that cooperate with contact segments 24 tap changing device 4. The even numbered ta s and contact segments cooperate with the winding 11, and'the odd'numbered tap connections and' contact segments cooperate with the winding 9. The drum 3a is connected, by a shaft 35, to a motor36 having a reversing switch 37 connected to its field winding 38. For controlling the direction of rotation of the motor 36, thereversing switch 37 may be either manually or automatically actuated by suitable circuits and apparatus which are not -h shown because they constitute no part of the present invention.

The protective system 5 comprises a current transformer 39, inductively related to one of the conductors of the secondary circuit 13, 7

and connected by conductors 41 and 4.2 to the several taps 43 to53 of an auto-transformer 54, whereby the current transformerBQ is in the-secondary circuit thereof. A second current transformer 56 is connected, by the conincluding the entire winding as the primary circuit and to the circuit including a portlon of the. winding as the secondary circuit. Accordingly, the entire windingis hereinafter called he primary winding and that portion of the inding included in both circuits .is

ductor 42 and a conductor 57 to the primary by conductors 7 7, to the motor 36.

The relay 59 may be of any desired typethat operate's when -subjected to a-predetermined current for a definite interval of time and comprises awinding'7 3 and a contactnaking device 7 4. v The contact-making device 74 is connected by conductors 75, to a battery 76 and the tripping coil 8 of the circuit interrupter 6. The battery 75 is also connected,

Assuming the tap-changing device 4 to be in such position that the taps 14 and 15 are in engagement with the contact segments 24 and 25, respectively, the main secondary circuit 13 is completed through the balance-coil 12 and the tap-changing device 4, at which time the contact segment 71 on the drum 61 is in engagement with the tap 52 of the auto-transformer 54. The primary winding 58 of the auto-transformer 54 is energized in accordance with the current traversing the main primary winding 2, while the secondary winding of the auto-transformer 54 includes all the windings above the tap 52. The main transformer 1 is now in its position of relatively low voltage and lightsecondary current, at which time the number of ampereturns in the primary winding of the transformer 54 equals the number of ampere-turnsin its secondary winding, with the result that the protective system 5 is in a-v state of equilibrium and no current traverses the re lay 59.

When it is desired to increase the secondary Voltage of the main transformer 1, the motor 36 is energized to turn the shaft 35 in a counter-elockwise direction which causes the several contact segments 25 to 33 to engage the tap connections 15 to 23, respectively, in a manner well known in the art, and to increase the voltage and, consequently, the secondary circuit in the main transformer 1. However, the current traversing the primary winding 2 of the main transformer 1 increases faster than the current traversing its secondary circuit 13. Accordingly, if the setting of the auto-transformer 54 were not changed, the influence of the current transformer 56 on the protective system would over-balance that of the primary-current transformer 39, with the result that the relay 59 would be operated to cause the circuit interrupter .6 to open, thereby deenergizing the main transformer 1.

In order to keep the influence of the current transformers 39 and 56 on the protective system 5 equal, it is necessary to so vary the tap connections 43 and 53 that, as the voltage of the secondary winding 3 of the transformer 1 is increased, the number of turns in the secondary circuit of the auto-transformer 54 is increased, so that p the number of ampere turns in the primary circuit of the auto-transformer 54 remains equal to the number of ampere-turns in its secondary circuit. This is accomplished by causing the drum 61 to successively move the contact segments 71 to 62-into engagement with the tap connections 52 to 43, respectively, in accordancc'with the movement of the drum 34 andthe contact segment carried thereby.-

Under normal operating conditions, the auto-transformer 54 remains ina state of balance or equilibrium, and the relay 59 remains deenergized. However, should a short-circuit occur between the turns of the primary Winding 2 or secondary winding 3, an increase in the amount of the primary current traversing the circuit 7 would occur, while the current traversing the secondary circuit 13 would not increase proportionately.

Thus a voltage is induced at the terminals of the secondary winding of the auto-transformer 54 by the current flowing in the primary winding due to the current transformer 56, which is greater than the voltage induced at the terminals of the secondary winding due to the current transformer 39. The result of this is that as'there is no longer balance a resultant voltage is applied to the relay 59.

Accordingly, therel-ay 59is energized to close its contact-making device 74, thereby actuating the tripping coil 8 to open the circuit interrupter 6.

When it is desired to reduce the secondary voltage of the transformer 1, the shaft 35 is turned in a clockwise direction, which causes the contact se ents on the drums 34 and 61 to engage thelr cooperation tap connections in a reverse order. However, the number of ampere-turns in the primary circuit of the transformer 54 is always maintained equal to the number of secondary ampere-turns, provided that no short-circuit exists between the turns ofthe main primary and secondary windings 2 and 3, respectively.

the ratio of its primary and secondary ampere-turns remams equal, regardless of changes in the ratio of the main primary and secondary currents of the protected trans-z former.

It is to be understood that such changes in the arrangement and connection of the component parts of my invention may be made as claims.

will be within the scope of the appended I claim as my invention: v 1. The combination with a transformer comprising primary and secondary windings, means for varying the number of effective turns of one ofthe windings, and a relay system responsive to predetermined diflerences in the current traversing the primary and secondary windings, of'means for regulating the relay system'i'n accordance with the operation 1 of the means for varying the winding.

2. The combination with a transformer comprls ng primary and secondary windings, means for varying the'number' of eifec tive turns of one of the windings, and a relay system responsive to predetermined differ- 2 upon the relay system in accordance with the for varying the windoperation of the means ing.

3. The combination with a transformer comprising primary and secondary windings,

means for varying the number of effective turns of one of the'windings, and a relay system responsive to predetermined differences in the current traversing the primary and secondary'windi-ngs,'of a contact making de vice for controlling the influence of the currents traversing the primary and secondary windings upon the relay system in accordvarying the winding.

4. The combination with a main transformer comprisin windings, means or varying the number of eifective turns of one of the windings, and a ance with :the operation of the means for relay system comprising a second transformer V 45 and a relay responsive to predetermined differences in the current traversing the main primary and secondary windings, of means for controlling the influence of the currents traversing the'main primary and secondary windings upon the relay by controlling the connections of the second transformer in accordance with the operation of the means for varying the winding.

5. The combination with a main transformer comprising primary and secondary windings, means for varying the number of eifective turns of one of the windings, and a relay system comprising an auto-transformer and a relay responsive to predetermined difprlmary and secondary ferences in-the current traversing the main primary and secondary windings, of means for-controlling the influence of the currents traversing the main primary and secondary windings upon the relay by controlling the connections of the auto-transformer in accordance with the operation of the means for varying the winding.

6. The combination with a transformer comprising primary and secondary windings, means for varying the number of effective turns of one of the windings, and a relay system responsive to predetermined differences in the current traversing the primary and secondary windings, and comprising an auxiliary transformer, and current transformers connected to the primary and secondary windings of the auxiliary transformer, of

means for controlling the influence of the currents traversing the first-named primary and secondary windings upon the relay system by controlling the connectionsof the auxiliary transformer in accordance with the operation of the means for varying one of the firstnamed windings.

7. The combination with a transformer comprising primary and secondary windings,

means for varying the, number of effective turns of one of the windings, and a relay system' responsive to predetermined diflerences in the current traversing the primary and secondary windings, and comprising an aux iliarytransformer and current transformers connected to both primary and secondary windings, respectively, of means for controlling the influence of the current traversing the first named primary and secondary wind ings upon the relay system by controlling the connections of the auxiliary transformer in accordancewith the operation of the means for varying one of the first named windings.

'8. The combination with a transformer comprising primary and secondary windings, means for varying the number of eflective turns of one of the windings, and a relay sys tem responsive to predetermined differences in the current traversing the primary and secondary windings, and comprising an auxiliary transformer and current transformers connected to both primary and secondary windings, respectively, of means for controlling the influence of the current traversing the first-named primary and secondary windings upon the relay system by varying the ratio between the primary and secondary windings of the auxiliary transformer in accordance with the operation of the means for varying one of the first-named windings.

i i HENRY 4A. TRAVERS. 

